'\" t
.\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\" References consulted:
.\"   GNU glibc-2 source code and manual
.\"   Dinkumware C library reference http://www.dinkumware.com/
.\"   OpenGroup's Single UNIX specification http://www.UNIX-systems.org/online.html
.\"
.TH wcsnrtombs 3 2024-06-15 "Linux man-pages 6.9.1"
.SH NAME
wcsnrtombs \- convert a wide-character string to a multibyte string
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <wchar.h>
.P
.BI "size_t wcsnrtombs(char " dest "[restrict ." len "], \
const wchar_t **restrict " src ,
.BI "                  size_t " nwc ", size_t " len ", \
mbstate_t *restrict " ps );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.BR wcsnrtombs ():
.nf
    Since glibc 2.10:
        _POSIX_C_SOURCE >= 200809L
    Before glibc 2.10:
        _GNU_SOURCE
.fi
.SH DESCRIPTION
The
.BR wcsnrtombs ()
function is like the
.BR wcsrtombs (3)
function,
except that the number of wide characters to be converted,
starting at
.IR *src ,
is limited to
.IR nwc .
.P
If
.I dest
is not NULL,
the
.BR wcsnrtombs ()
function converts
at most
.I nwc
wide characters from
the wide-character string
.I *src
to a multibyte string starting at
.IR dest .
At most
.I len
bytes are written to
.IR dest .
The shift state
.I *ps
is updated.
The conversion is effectively performed by repeatedly
calling
.IR "wcrtomb(dest, *src, ps)" ,
as long as this call succeeds,
and then incrementing
.I dest
by the
number of bytes written and
.I *src
by one.
The conversion can stop for three reasons:
.IP \[bu] 3
A wide character has been encountered that can not be represented as a
multibyte sequence (according to the current locale).
In this case,
.I *src
is left pointing to the invalid wide character,
.I (size_t)\ \-1
is returned,
and
.I errno
is set to
.BR EILSEQ .
.IP \[bu]
.I nwc
wide characters have been
converted without encountering a null wide character (L\[aq]\[rs]0\[aq]),
or the length limit forces a stop.
In this case,
.I *src
is left pointing
to the next wide character to be converted, and the number of bytes written
to
.I dest
is returned.
.IP \[bu]
The wide-character string has been completely converted, including the
terminating null wide character (which has the side effect of bringing back
.I *ps
to the initial state).
In this case,
.I *src
is set to NULL, and the number
of bytes written to
.IR dest ,
excluding the terminating null byte (\[aq]\[rs]0\[aq]), is
returned.
.P
If
.I dest
is NULL,
.I len
is ignored,
and the conversion proceeds as above,
except that the converted bytes are not written out to memory, and that
no destination length limit exists.
.P
In both of the above cases,
if
.I ps
is NULL, a static anonymous
state known only to the
.BR wcsnrtombs ()
function is used instead.
.P
The programmer must ensure that there is room for at least
.I len
bytes
at
.IR dest .
.SH RETURN VALUE
The
.BR wcsnrtombs ()
function returns
the number of bytes that make up the
converted part of multibyte sequence,
not including the terminating null byte.
If a wide character was encountered which
could not be converted,
.I (size_t)\ \-1
is returned, and
.I errno
set to
.BR EILSEQ .
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lb lb lbx
l l l.
Interface	Attribute	Value
T{
.na
.nh
.BR wcsnrtombs ()
T}	Thread safety	T{
.na
.nh
MT-Unsafe race:wcsnrtombs/!ps
T}
.TE
.SH STANDARDS
POSIX.1-2008.
.SH NOTES
The behavior of
.BR wcsnrtombs ()
depends on the
.B LC_CTYPE
category of the
current locale.
.P
Passing NULL as
.I ps
is not multithread safe.
.SH SEE ALSO
.BR iconv (3),
.BR mbsinit (3),
.BR wcsrtombs (3)
